All Weather News

NWS Implements Tiered Severe Thunderstorm Warnings

2 Aug 2021, 12:00 pm

Severe Thunderstorm Warnings issued by the National Weather Service (NWS) will include language with new “damage threat categories,” including “considerable” and “destructive.” Previously, only tornado warnings (TOR) had a sub-category to indicate a potential level of destruction including “considerable” and “catastrophic” starting today, August 2nd, 2021.

Special Weather Statements, issued for sub-severe storms, will also be updated to be more similar to the format of current warnings for severe storms.

These new categories will be included as a part of the Impact-Based Warning (IBW) coded tags at the bottom of the product and are being changed to highlight a storm’s potential impact in a format that can be quickly read and understood.

The lower end of severe thunderstorms will not receive the verbiage “considerable” or “destructive,” but will continue to include the damage threat tag with hail and wind amounts as they appear in the operational product.

The following criteria will have to be met for a storm to garner the new tags:

CONSIDERABLE…1.75 inch diameter hail (golf ball-sized) and/or 70 mph thunderstorm

DESTRUCTIVE…2.75 inch + diameter hail (baseball-sized) and/or 80+ mph thunderstorm

The other notable change to the IBW tag will be the language used to describe the maximum potential threat of hail or wind in a storm.

Previously, warnings indicated a maximum potential wind speed or hail size next to the word “hail” or “wind.” An example of the current format has been posted below.

With the upgrade, these tags will now appear as follows.

Each category will now have a word indicating whether the hazard has been observed or is based on radar data. The size or speed of the threat will then be indicated after the word “max hail size” or “max wind gust.”

The changes are expected to be implemented on or around the 28th of April, according to this release from the National Weather Service.

Severe thunderstorms that receive the “destructive” tag will be recommended to activate a Wireless Emergency Alert (WEA) for mobile devices in the area.

This new system was proposed during the summer of 2020.

The full write up on the proposed changes can be viewed here.

About the author
Alana Cameron was born and raised in Canada in the city of Mississauga, just outside of Toronto. Alana is the oldest of 4 siblings, all close in age, and grew up playing outside with them in all types of weather. After graduating high school, Alana moved to study at the University of British Columbia in Kelowna for a year before transferring to Dalhousie University in Halifax, Nova Scotia where sh... Load Moree completed a Bachelor of Science in Physics and Atmospheric Science. Upon completion, Alana moved back to Toronto where she completed a post-grad degree in Meteorology at York University. After her post-grad, she went on to complete another post-grad in Broadcast Journalism - TV News at Fanshawe College in London, Ontario. During her final year of studies she had the privilege of interning with the best in the business in Canada at The Weather Network. Once she finished her internship, she got the call from small-town Denison, Texas where she accepted a job as an on-air meteorologist at KTEN-TV, right in tornado alley, covering severe weather from Sherman/Denison (North Texas) to Ada (Southern Oklahoma). After the most active tornado season Oklahoma had seen in May 2019 (105 tornadoes!) Alana is excited to join WeatherNation to cover weather all across the nation. If you're interested in following her on social media she can be found @alanacameronwx!